Display device and method for manufacturing the same

ABSTRACT

Provided are a display device and a method of manufacturing the same. A display device includes a coplanar thin-film transistor and a capacitor. The coplanar thin-film transistor comprises a gate electrode, an active layer including an oxide semiconductor, a source electrode and a drain electrode. The capacitor comprises a lower electrode, intermediate electrode and upper electrode. And the lower electrode is comprised of the same material as the active layer, and is conductivized. Also, the upper electrode is connected to the lower electrode. By using the conductivized lower electrode, the capacitor is configured to operate as multiple capacitors. Thus, the size of the capacitor is reduced, and sufficient capacitance may be secured with the capacitor with a smaller area. In this way, the area of each sub-pixel in the display device may be reduced, thereby achieving high resolution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2013-0120127 filed on Oct. 8, 2013, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure is directed to a display device and a method ofmanufacturing the same, and specifically to a display device that cancontrol stable capacitance of a storage capacitor as the storagecapacitor with a smaller size, and a method of manufacturing the same.

Description of the Related Art

A display device driven in an active-matrix type includes a thin-filmtransistor in each of sub-pixels, and a liquid crystal layer or anorganic light-emitting element depending on the type of the displaydevice. Further, each of the sub-pixels includes a storage capacitor tocontrol data voltage stably. In a display device including a liquidcrystal layer, the storage capacitor can maintain data voltage stably,that is, a voltage difference between a pixel electrode and a commonelectrode. In a display device including an organic light-emittingelement, the storage capacitor can maintain data voltage stably, thatis, a voltage difference between the gate electrode and the sourceelectrode, or the gate electrode and the drain electrode, of a drivingtransistor.

SUMMARY OF THE INVENTION

As the area of each sub-pixel is reduced in order to achieve higherresolution of a display device, the size of a thin-film transistor (TFT)or a storage capacitor in each of sub-pixels is reduced. This results indecrease in capacitance of the storage capacitor. When this happens, thedata voltage in a sub-pixel becomes unstable. Therefore, sufficientcapacitance of the storage capacitor should be secured.

The storage capacitor needs a certain minimal size in order to securethe capacitance. The inventors of the present disclosure have developeda display device with minimized size of the storage capacitor whilemaintaining capacitance to supply stable data voltage via using an oxidesemiconductor as an electrode of the storage capacitor. Also, a methodof manufacturing the display device is disclosed.

An object of the present disclosure is to provide a storage capacitorhaving the same capacitance with a conventional storage capacitor,though the size of the storage capacitor is smaller than that of theconventional storage capacitor. This results in reduction of the area ofa sub-pixel, hence, an increase of the number of sub-pixels per unitarea, and thus provision of a display device having higher resolution.

Further, another object of the present disclosure is to provide atransparent organic light-emitting display device with a storagecapacitor having a smaller size than that of the conventional storagecapacitor. Thus the transmittance of the transparent organiclight-emitting display device is improved, since the size oflight-emitting region with the storage capacitor decreases and the sizeof light-transmissive region without the storage capacitor increases.Further, a method of manufacturing the same is disclosed.

Objects of the present disclosure are not limited to those describedabove. Other objects not described herein will be clearly understood bya person skilled in the art from the following description.

According to an aspect of the present disclosure, there is provided adisplay device capable of achieving above-mentioned objects. The displaydevice includes a substrate, a coplanar thin-film transistor, and astorage capacitor. The coplanar thin-film transistor includes an activelayer including an oxide semiconductor, a gate electrode, and a sourceor drain electrode. The storage capacitor comprises a lower electrode, afirst insulation layer, an intermediate electrode, a second insulationlayer, and an upper electrode. And the lower electrode is comprised ofthe same material as the active layer, and is conductivized.

By using the conductivized lower electrode, the storage capacitor isconfigured to operate as multiple capacitors. Thus, the size of thestorage capacitor is reduced. In addition, sufficient capacitance may besecured with the storage capacitor with a smaller size. In this way, thearea of each sub-pixel in the display device may be reduced, therebyachieving high resolution.

When the display device is a transparent organic light-emitting displaydevice, the smaller size of the storage capacitor allows for reductionof an size of a light-emitting region and relatively for increase of ansize of a light-transmissive region. Thus, the transmittance of thetransparent organic light-emitting display device is improved.

According to an exemplary embodiment of the present disclosure, a layercomprised of the same material as an active layer is patterned using ahalf-tone mask, and is conductivized. Thus, the number of processes formanufacturing the display device can be minimized.

Other particulars of exemplary embodiments are illustrated in thedetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A is a cross-sectional view of a display device according to anexemplary embodiment of the present disclosure;

FIG. 1B is a cross-sectional view of an organic light-emitting displaydevice according to an exemplary embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of an organic light-emitting displaydevice according to an exemplary embodiment of the present disclosure;

FIG. 3 is a simplified plan view of a display device according to anexemplary embodiment of the present disclosure;

FIG. 4 is a flowchart for illustrating a method of manufacturing anorganic light-emitting display device according to an exemplaryembodiment of the present disclosure; and

FIGS. 5A to 5F are cross-sectional views each illustrating a processingstep for manufacturing an organic light-emitting display deviceaccording to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Various advantages and features of the present invention and methodsaccomplishing thereof will become apparent from the followingdescription of embodiments with reference to the accompanying drawings.However, the present invention is not limited to exemplary embodimentdisclosed herein but will be implemented in various forms. The exemplaryembodiments are provided by way of example only so that a person ofordinary skilled in the art can fully understand the disclosures of thepresent invention and the scope of the present invention. Therefore, thepresent invention will be defined only by the scope of the appendedclaims.

Indicating that elements or layers are “on” other elements or layersinclude both a case in which the corresponding elements are just aboveother elements and a case in which the corresponding elements areintervened with other layers or elements. Indicating that elements orlayers are “directly on” other elements or layers means a case in whichthe corresponding elements are just above other elements.

The same reference numerals indicate the same elements throughout thespecification.

In the drawings, size and thickness of each element are arbitrarilyillustrated for convenience of description, and the present invention isnot necessarily limited to those illustrated in the drawings.

Although first, second, and the like are used in order to describevarious components, the components are not limited by the terms. Theabove terms are used only to discriminate one component from the othercomponent. Therefore, a first component mentioned below may be a secondcomponent within the technical spirit of the present invention.

Respective features of various exemplary embodiments of the presentinvention can be partially or totally joined or combined with each otherand as sufficiently appreciated by those skilled in the art, variousinterworking or driving can be technologically achieved and therespective exemplary embodiments may be executed independently from eachother or together executed through an association relationship.

FIG. 1A is a cross-sectional view of a display device according to anexemplary embodiment of the present disclosure. A display device 100Aincludes a coplanar thin-film transistor T and a storage capacitor Cst.

A substrate 110 includes a region A in which the coplanar thin-filmtransistor T is formed and a region B in which the storage capacitor Cstis formed. In the region A of the substrate 110, an active layer 131, agate insulation layer 112, a gate electrode 132, an inter-insulationlayer 113, a source electrode 133, and a drain electrode 134 are stackedon one another, to form the coplanar thin-film transistor T. In theregion B of the substrate 110, a lower electrode 121, a first insulationlayer 116, an intermediate electrode 122, a second insulation layer 117,and an upper electrode 123 are stacked on one another, to form thestorage capacitor Cst. The lower electrode 121, the first insulationlayer 116, the intermediate electrode 122, and the second insulationlayer 117, and the upper electrode 123 in the region B may be formed ofthe same materials and in the same processes as the active layer 131,the gate insulation layer 112, the gate electrode 132, theinter-insulation layer 113, the source and the drain electrodes 133 and134 in the region A, respectively.

A buffer layer 111 is formed on the substrate 110. The buffer layer 111may reduce permeation of moisture or impurities through the substrate110, and may make a surface of the substrate flat. The buffer layer 111may be formed of a silicon oxide film, a silicon nitride film or a duallayer thereof. On the buffer layer 111, the coplanar thin-filmtransistor T and the storage capacitor Cst is formed.

In the following description, the configuration of the coplanarthin-film transistor T formed in the region A of the substrate 110 willbe described first and then that of the storage capacitor Cst formed inthe region B will be described.

The active layer 131 including an oxide semiconductor is formed in theregion A of the substrate 110. The oxide semiconductor included in theactive layer 131, for example, may be comprised ofindium-gallium-zinc-oxide (InGaZnO) based material. The active layer 131includes a source region, a drain region, and a channel region. Thesource region and the drain region of the active layer 131 may beconductivized for better contact efficiency with the source electrode133 and the drain electrode 134, respectively.

Referring to FIG. 1A, the channel region of the active layer 131overlapping and below the gate electrode 132 is an oxide semiconductor,while the source region in contact which the source electrode 133 andthe drain region in contact with the drain electrode 134 are regionswhere an oxide semiconductor is conductivized. As used herein, it isassumed that the active layer 131 includes all of the conductivizedsource region, the conductivized drain region, and the channel region.As used herein, the expression “X is conductivized” does not mean thatthe X becomes a complete conductor, but means that it has a propertysimilar to a conductor. For example, the “oxide semiconductor isconductivized” means that the surface resistivity of the oxidesemiconductor became 10³ Ω/□ (ohm per square) or smaller.

The gate insulation layer 112 is formed on the active layer 131. Thegate insulation layer 112 insulates the gate electrode 132 from theactive layer 131. The gate insulation layer 112 may be formed of, but isnot limited to, a silicon oxide film, a silicon nitride film or a duallayer thereof. In some embodiments, the gate insulation layer 112 may beformed only on the active layer 131 overlapping and below the gateelectrode 132. In some other embodiments, the gate insulation layer 112may be formed over the entire surface of the substrate 110.

The gate electrode 132 is formed on the gate insulation layer 112. Atleast a part of the gate electrode 132 is overlapped and above theactive layer 131. The gate electrode 132 may be formed of a conductivematerial.

The inter-insulation layer 113 may be formed on the gate electrode 132.The inter-insulation layer 113 may be formed of the same material as thegate insulation layer 112. The inter-insulation layer 113 is formed overthe entire surface of the substrate 110, and the source electrode 133and the drain electrode 134 is electrically connected to the activelayer 131 via contact holes formed in the inter-insulation layers 113.

The source electrode 133 and the drain electrode 134 are formed on theinter-insulation layer 113. The source electrode 133 and the drainelectrode 134 is contact with the active layer 131 via the contact holesformed in the inter-insulation layer 113, respectively. To be specific,the source electrode 133 is in contact with the source region of theactive layer 131, and the drain electrode 134 is in contact with thedrain region of the active layer 131. The source and the drain electrode133 and 134 may be formed of conductive materials.

Now, the configuration of the storage capacitor Cst formed in the regionB of the substrate 110 will be described.

The lower electrode 121 of the storage capacitor Cst is formed at thesame plane as the active layer 131 of the coplanar thin-film transistorT on the substrate 110. The lower electrode 121 may be formed of thesame oxide semiconductor material as the active layer 131. Also, thelower electrode 121 may be formed by patterning the same oxidesemiconductor material as the active layer 131 to a desired size, andthen conductivizing it.

The first insulation layer 116 is formed on the lower electrode 121. Thefirst insulation layer 116 insulates the intermediate electrode 122 fromthe lower electrode 121 and serves as a dielectric in a first capacitorC1 between the lower electrode 121 and the intermediate electrode 122.In addition, the first insulation layer 116 may be formed ofsubstantially the same material or may be the same layer as theabove-described gate insulation layer 112. When the first insulationlayer 116 is the same layer as the gate insulation layer 112, the numberof processes may be reduced compared to when the gate insulation layer112 and the first insulation layer 116 are separately formed.

The first insulation layer 116 is to insulate the intermediate electrode122 from the lower electrode 121. Thus, as illustrated in the FIG. 1A,the first insulation layer 116 is formed only on the lower electrode121. But, the present disclosure is not limited thereto. The firstinsulation layer 116 may be formed over the entire surface of thesubstrate 110.

The intermediate electrode 122 is positioned on the first insulationlayer 116. At least apart of the intermediate electrode 122 isoverlapped the lower electrode 121. The intermediate electrode 122 maybe formed of a conductive material and may be formed of the samematerial as the above-described gate electrode 132. The intermediateelectrode 122 may be electrically connected to the gate electrode 132.

In the display device 100A according to the exemplary embodiment of thepresent disclosure, the intermediate electrode 122, the first insulationlayer 116 and the lower electrode 121 form the first capacitor C1 havingfirst capacitance.

Capacitance is in inverse proportion to the thickness of a dielectricbetween two electrodes of a capacitor. Accordingly, the firstcapacitance of the first capacitor C1 is in inverse proportion to thethickness of the first insulation layer 116. Thus, the first insulationlayer 116 may be formed as thin as possible in order to increase thefirst capacitance. The first insulation layer 116 may be formed of thesame material as the gate insulation layer 112 but may have differentthickness from the gate insulation layer 112. For example, the firstinsulation layer 116 may be thinner than the gate insulation layer 112.That is, the distance from the lower electrode 121 to the intermediateelectrode 122 may be shorter than the distance between the active layer131 to the gate electrode 132. Reducing the thickness of the firstinsulation layer 116 can increase the capacitance of the first capacitorC1.

The second insulation layer 117 may be formed on the intermediate layer122. The second insulation layer 117 insulates the upper electrode 123from the intermediate electrode 122 and serves as a dielectric in asecond capacitor C2 between the intermediate electrode 122 and the upperelectrode 123. The second insulation layer 117 may be formed of the samematerial and formed in the same layer as the above-describedinter-insulation layer 113. The number of processes may be reduced byforming the second insulation layer 117 and the inter-insulation layer113 together in a single step.

The upper electrode 123 is positioned on the second insulation layer117. At least a part of the upper electrode 123 is overlapped theintermediate electrode 122. The upper electrode 123 may be formed of aconductive material and may be formed of the same material as theabove-described source electrode 133 or the drain electrode 134. In FIG.1A, the upper electrode 123 is connected to the lower electrode 123.

Also, in FIG. 1A, the upper electrode 123 is connected with the drainelectrode 134 of the coplanar thin-film transistor T. However, in someother embodiments, the upper electrode 123 may be connected to thesource electrode 133 depending on the type and the operation conditionsof the coplanar thin-film transistor T.

In the display device 100A according to the exemplary embodiment of thepresent disclosure, the intermediate electrode 122, the secondinsulation layer 117 and the upper electrode 123 form a second capacitorC2 having second capacitance.

The second insulation layer 117 may be reduced in order to increase thesecond capacitance. The second insulation layer 117 may be formed of thesame material as the inter-insulation layer 113 but may have a thicknessdifferent from the inter-insulation layer 113. For example, the secondinsulation layer 117 may be thinner than the inter-insulation layer 113.That is, the distance from the intermediate electrode 122 to the upperelectrode 123 may be shorter than the distance between the gateelectrode 132 to the source electrode 133 or the distance between thegate electrode 132 to the drain electrode 134. When the secondinsulation layer 117 is thinner than the inter-insulation layer 113, thesecond capacitor C2 may have capacitance larger than that when thesecond insulation layer 117 and the inter-insulation layer 113 have thesame thickness.

The first capacitor C1 comprises the lower electrode 121, the firstinsulation layer 116 and the intermediate electrode 122. The secondcapacitor C2 comprises the upper electrode 123, the second insulationlayer 117, and the intermediate electrode 122. The lower electrode 121and the upper electrode 123 are connected to each other such that thefirst capacitor C1 and the second capacitor C2 are connected to eachother in parallel to operate as a one storage capacitor Cst.

When the first insulation layer 116 may be formed simultaneously withthe gate insulation layer 112, the thickness of the first insulationlayer 116, which sets the first capacitance of the first capacitor C1,may be the same as that of the gate insulation layer 112. Similarly, thesecond capacitance of the second capacitor C2 may be affected by thethickness of the inter-insulation layer 113 when the second insulationlayer 117 is formed simultaneously with the inter-insulation layer 116.

When forming the coplanar thin-film transistor T, the gate insulationlayer 112 may be thinner than the inter-insulation layer 113. In suchcases, the first insulation layer 116 may be thinner than the secondinsulation layer 117, and the first capacitance may be larger than thesecond capacitance.

By configuring the storage capacitor Cst as illustrated in FIG. 1A, thesize of the storage capacitor Cst can be reduced while providing atleast the same or greater capacitance than the conventional storagecapacitor configuration. With the reduced size of the storage capacitorCst, the area of each of sub-pixels can be reduced. This can increasethe number of sub-pixels per unit area, thereby achieving a higherresolution in a display device.

Referring to FIG. 1A, a coplanar thin-film transistor T has a structurein which a source electrode 133, a drain electrode 134, and a gateelectrode 132 are formed above an active layer 131. On the contrary, astaggered thin-film transistor has a structure in which a gateelectrode, an insulation layer, an active layer, and a source electrodeand a drain electrode are formed in order. In this setting, the sourceand drain electrodes are electrically connected to the active layerwithout an additional insulation layer therebetween, which makes itdifficult to form a capacitor by conductivizing a portion of thesemiconductor layer.

In order to utilize a portion of the semiconductor layer as anindependent electrode for the capacitor in the staggered thin-filmtransistor, it is necessary to form the additional insulation layer onthe active layer and to conduct an additional opening process.Therefore, when conductivizing a portion of the semiconductor layer toutilize it as the electrode of the capacitor, the coplanar thin-filmtransistor T is advantageous over the staggered thin-film transistor.

FIG. 1B is a cross-sectional view of an organic light-emitting displaydevice according to an exemplary embodiment of the present disclosure.Among the elements of the organic light-emitting display device 100Billustrated in FIG. 1B, redundant descriptions on the elementssubstantially the same as those in FIG. 1A will not be made.

Referring to FIG. 1B, an organic light-emitting element including ananode 141, an organic light-emitting layer 143 and a cathode 144 isformed on a planarization layer 118. The organic light-emitting layer143 may be formed on the anode 141, and the cathode 144 may be formed onthe organic light-emitting layer 143. The anode 141 is electricallyconnected to a drain electrode 134 of a coplanar thin-film transistor Tvia a contact hole in the planarization layer 118, and a bank layer 142covers the contact hole. That is, the anode 141 is electricallyconnected to the upper electrode 123 and the drain electrode 134.Although not depicted in FIG. 1B, the stepped portion in the anode 141due to the contact hole may cause light leakage from the sub-pixel. Inorder to reduce this, the bank layer 142 may be formed to cover thecontact hole. In this manner, the visibility of the organiclight-emitting display device 100B can be improved.

In the organic light-emitting display device 100B according to theexemplary embodiment of the present disclosure, a portion of an oxidesemiconductor layer formed on the same plane as an active layer 131 ofthe coplanar thin-film transistor T is conductivized to serve as a lowerelectrode 121 of a storage capacitor Cst. On the lower electrode 121, afirst insulation layer 116, an intermediate electrode 122, a secondinsulation layer 117 and an upper electrode 123 are stacked in thestated order to form the storage capacitor Cst. Accordingly, the storagecapacitor Cst with sufficient capacitance may be formed even in alimited area thereof.

When the storage capacitor Cst is configured as illustrated in FIG. 1B,the same capacitance can be obtained from the storage capacitor Cst evenwhen it has a smaller size than a conventional storage capacitor. Usingthe smaller storage capacitor Cst, the area of each of sub-pixels can bereduced and thus the number of sub-pixels per unit area can beincreased. This results in a display device with higher resolution.

In some embodiments, the display device may be a bottom emission typeorganic light-emitting display device. In such embodiments, the size ofthe light-emitting region excluding the size of the storage capacitorCst can be enlarged by employing the storage capacitor Cst illustratedin FIG. 1B.

The organic light-emitting display device 100B according to theexemplary embodiment of the present disclosure may include a pluralityof sub-pixels, and the sub-pixels may respectively include at least acoplanar thin-film transistor T and at least a storage capacitor Cst.Also, the storage capacitor Cst in at least one of the plurality ofsub-pixels has a size that is different from the size of the storagecapacitor in another sub-pixel. In the organic light-emitting displaydevice 100B, sub-pixels may require different currents for driving,respectively. The sizes of the storage capacitors Cst included in thedifferent sub-pixels may be designed based on the different drivingcurrents. By designing the storage capacitors Cst having differentsizes, the efficiency of the storage capacitor Cst in each of thesub-pixels can be maximized, and a space for an additional thin-filmtransistor can be obtained, if necessary.

FIG. 2 is a cross-sectional view of a display device 200 according to anexemplary embodiment of the present disclosure. Elements of the displaydevice 200 illustrated in FIG. 2, corresponding to the elements in FIG.1A will not be described again for simplicity.

Referring to FIG. 2, a third insulation layer 215 is formed on an upperelectrode 223, a source and a drain electrodes 233 and 234. A connectionpart 235A and an additional electrode 235B are formed on the thirdinsulation layer 215. The third insulation layer 215 may be formed of amaterial that may serve as a dielectric layer between the upperelectrode 223 and the additional electrode 235B. The third insulationlayer 215 may be formed of a silicon oxide film, a silicon nitride filmor multiple layers thereof. The connection part 235A is arranged tooverlap with the drain electrode 234, and at least a part of theadditional electrode 235B is arranged to overlap with the upperelectrode 223. The connection part 235A is electrically connected to thedrain electrode 234. The connection part 235A and the additionalelectrode 235B may be formed of a conductive material. In someembodiments of the present disclosure, the connection part 235A may beomitted.

The additional electrode 235B and the upper electrode 223 form a thirdcapacitor C3 with the third insulation layer 215 serving as a dielectriclayer.

The third capacitor C3 is connected to the first capacitor C1 and thesecond capacitor C2 in parallel, to configure a storage capacitor Cst.In other words, the first capacitor C1 comprises the lower electrode221, the first insulation layer 216 and the intermediate electrode 222.The second capacitor C2 comprises the upper electrode 223, the secondinsulation layer 217 and the intermediate electrode 222. Also, the thirdcapacitor C3 comprises the upper electrode 223, the third insulationlayer 215, and the additional electrode 235B. Here, the upper electrode223 is connected to the lower electrode 221, and the additionalelectrode 235B is connected to intermediate electrode 222. In this way,the storage capacitor Cst may operate like three capacitors connected toone another in parallel.

By forming the third capacitor C3 connected in parallel, the storagecapacitor Cst may provide larger capacitance without increasing the sizeof the storage capacitor Cst. Moreover, since sufficient capacitance canbe obtained without enlarging the size of the storage capacitor, thearea of a sub-pixel can be reduced to increase the number of sub-pixelsper unit area. This leads to providing a display device with higherresolution.

FIG. 3 is a simplified diagram for illustrating a transparent organiclight-emitting display device according to an exemplary embodiment ofthe present disclosure.

As used herein, the transparent organic light-emitting display device300 refers to a display device provided with a certain transmittance,which enables a user to see through the transparent organiclight-emitting display device 300. For example, the transmittance of thetransparent organic light-emitting display device 300 may be equal to orhigher than 20%.

Referring to FIG. 3, each of the sub-pixels may include alight-transmissive region TA and a light-emitting region EA. Thelight-emitting region EA may include a switching transistor TFT1, adriving transistor TFT2 and a storage capacitor Cst. Thelight-transmissive region TA allows light from the outside to passthrough it. Therefore, if the transistors TFT1 and TFT2 and the storagecapacitor Cst are formed in the light-transmissive region TA, thetransmittance of the transparent organic light-emitting display device300 decreases and thus a user may not be able to clearly recognize anobject through the display device. For this reason, the transistors TFT1and TFT2 and the storage capacitor Cst may be positioned in thelight-emitting region EA, as illustrated in FIG. 3.

In the organic light-emitting display device 300 according to theexemplary embodiment of the present disclosure, the storage capacitorCst is formed in a following manner. The lower electrode of the storagecapacitor is formed by conductivizing the oxide semiconductor layer thatserves as the active layers of the transistors TFT1 and TFT2. The firstinsulation layer, the intermediate electrode, and the second insulationlayer, and the upper electrode are stacked on the lower electrode inthis order. The first capacitor C1 includes a lower electrode, a firstinsulation layer, and an intermediate electrode. And the secondcapacitor C2 includes an upper electrode, a second insulation layer, andan intermediate electrode. The first capacitor C1 and the secondcapacitor C2 may be connected to each other in parallel and may behaveas one storage capacitor Cst. The storage capacitor Cst comprised ofcapacitors C1 and C2 may be formed with an size equal to or smaller thantwo-thirds of the size of a conventional storage capacitor having thesame capacitance as the storage capacitor Cst. Also, the size of thestorage capacitor Cst may be equal to or smaller than 20% of the size ofone sub-pixel.

Since the storage capacitor Cst in the transparent organiclight-emitting display device 300 may be implemented with a smaller sizethan the conventional storage capacitor having the equal capacitancethereto, the area of the light-emitting region EA can be reduced. Thus,the area of the light-transmissive region TA can increase relatively ina sub-pixel, and, hence, the transmittance of the transparent organiclight-emitting display device 300 can increase. Further, even when thearea of the light-transmissive region TA does not increase, the area ofa sub-pixel can be reduced so that the number of sub-pixels per unitarea can be increased. This results in increasing the resolution of thetransparent organic light-emitting display device 300. Although thestorage capacitor illustrated in FIG. 3 is configured by connecting twocapacitors to each other in parallel, the configuration of the storagecapacitor is not limited thereto but may be configured by connectingthree or more capacitors to one another in parallel.

In order to improve the reliability of an organic light-emitting displaydevice, various thin-film transistors may be added thereto. Forinstance, an initialization thin-film transistor, a discharge thin-filmtransistor, an internal compensation thin-film transistor, a thresholdvoltage (Vth) compensation thin-film transistor, a sampling thin-filmtransistor, an emission thin-film transistor and the like may be addedthereto.

In various exemplary embodiments of the present disclosure, thelight-emitting region EA of a transparent organic light-emitting displaydevice 300 has limited space, and, thus, the above-described variousthin-film transistors and the storage capacitor may not be included dueto the limited space. In particular, since the capacitance of thestorage capacitor Cst is proportional to the size of the storagecapacitor Cst, sufficient space is necessary in order to securecapacitance to drive the transparent organic light-emitting displaydevice 300. As for the storage capacitor Cst according to an exemplaryembodiment of the present disclosure, an active layer is conductivizedso as to be employed as an electrode for multiple storage capacitorsCst. Thus, sufficient capacitance can be secured even in small space andthus additional thin-film transistors can be included.

FIG. 4 is a flowchart for illustrating a method of manufacturing adisplay device according to an exemplary embodiment of the presentdisclosure. FIGS. 5A to 5F are cross-sectional views each illustrating aprocessing step for manufacturing a display device according to anexemplary embodiment of the present disclosure.

According to the method of manufacturing a display device according tothe exemplary embodiment of the present disclosure, a coplanar thin-filmtransistor T and a storage capacitor Cst may be formed in a sub-pixel ofthe display device.

Initially, an oxide semiconductor layer 530 is formed on the substrate510 (S100). Subsequently, the oxide semiconductor layer 530 is patternedusing a half-tone mask 501 to form an active layer 530A and a lowerelectrode portion 530B (S200).

Referring to FIG. 5A, the buffer layer 511, the oxide semiconductorlayer 530, and a photoresist layer 540 are stacked on one another inthis order on the substrate 510. The half-tone mask 501 may include ablock portion 502 blocking light, a transmissive portion 503 allowingfor light to pass therethrough, and a translucent portion 504 allowingfor partial light to pass therethrough. After the half-tone mask 501 isdisposed on the photoresist layer 540, exposure process is performedfollowed by a development process.

As can be seen from FIG. 5B, after the development process, aphotoresist 541A in a region corresponding to the transmissive portion503 remains, and a photoresist 541B in a region corresponding to thetranslucent portion 504 partially remains.

Referring to FIG. 5C, etching process is performed to remove the oxidesemiconductor layer 530 where the photoresists 541A and 541B do notremain. After etching process, in the oxide semiconductor layer 530, theregion corresponding to the transmissive portion 503 is referred to asthe active layer 530A, and the region corresponding to the translucentportion 504 is referred to as the lower electrode portion 530B. Theactive layer 530A is spaced apart from the lower electrode portion 530B.

Subsequently, as shown in FIG. 5D, a part of the photoresist 541A on theactive layer 530A and the photoresist 541B on the lower electrodeportion 530B are removed by ashing process. After ashing process, thephotoresist 541B is removed to expose the lower electrode portion 530B,and a part of photoresist 541A remains on the active layer 530A.

Then, the lower electrode portion 530B is conductivized to form a lowerelectrode 521 of a storage capacitor Cst S. Conductivizing process mayinclude performing drying etching, hydrogen plasma treatment, heliumplasma treatment and the like on the lower electrode portion 530B. Theactive layer 530A where the photoresist 541A remains is notconductivized. Subsequently, the photoresist 541A remaining on theactive layer 530A is stripped.

The patterning process and the conductivizing process of the oxidesemiconductor layer 530 illustrated in FIGS. 5A to 5D may be conductedby using various processes other than the process with the half-tonemask 501. For example, the oxide semiconductor layer 530 may bepatterned or conductivized using two photo masks instead of thehalf-tone mask 501.

Then, referring to FIG. 5E, a gate insulation layer 512A is formed onthe active layer 530A, and a first insulation layer 512B is formed onthe lower electrode 521. The gate insulation layer 512A and the firstinsulation layer 512B may be formed of the same material. And the firstinsulation layer 512B may be formed simultaneously with the gateinsulation layer 512A. Thus, the first insulation layer 512B and gateinsulation layer 512 may be referred to as a base insulation layer.

A gate electrode 532 is formed on the gate insulation layer 512A, and anintermediate electrode 522 is formed on the first insulation layer 512B.In other words, the gate electrode 532 and the intermediate electrode522 are formed on the base insulation layer. The gate electrode 532 maybe formed of the same material as the intermediate electrode 522. Forexample, a first conductive layer is deposited on the base insulationlayer, and then, the first conductive layer is patterned to form thegate electrode 532 and the intermediate electrode 522 spaced apart fromthe gate electrode 532. The gate electrode 532 overlaps with at least apart of the active layer 530A. The intermediate electrode 522 overlapsat least a part of the lower electrode 521.

In addition, exposed portions of the active layer 530A are conductivized(S500). The exposed portions of the active layer 530A mean the portionswhere the active layer 530A is not overlapped with the gate electrode532 or the gate insulation layer 512A. Herein, conductivizing theexposed portions of the active layer 530A may be performed separatelyfrom conductivizing the lower electrode portion 530B for forming theabove described lower electrode 521. However, the process forconductivizing the exposed portions of the active layer 530A and theprocess for conductivizing the lower electrode portion 530B may beperformed simultaneously.

Then, referring to FIG. 5F, an additional insulation layer 513 is formedover the gate electrode 532 and the intermediate electrode 522. To bespecific, an inter-insulation layer is formed on the gate electrode 532,and a second insulation layer is formed on the intermediate electrode522. The second insulation layer may be formed simultaneously withinter-insulation layer. Thus, the inter-insulation layer and the secondinsulation layer may be referred to as the additional insulation layer513.

A source electrode 533 and a drain electrode 534 are formed over theactive layer 530A. Further, an upper electrode 523 is formed over theintermediate electrode 522 (S600). Also, the source electrode 533, thedrain electrode 534 and the upper electrode 523 are formed on theadditional insulation layer 513. The upper electrode 523 may be formedof the same material as the source electrode 533 and the drain electrode534. For example, a second conductive layer is deposited on theadditional insulation layer 513. And then, the second conductive layeris patterned to form the source and drain electrodes 533 and 534 and theupper electrode 523.

The source electrode 533 and the drain electrode 534 are electricallyconnected to the conductivized regions of the active layer 530A viacontact holes in the additional insulation layer 513, respectively. Theupper electrode 523 is connected to the lower electrode 521 via acontact hole in the additional insulation layer 513. Although the drainelectrode 534 and the upper electrode 523 are illustrated as beingelectrically connected to each other in FIG. 5F, the upper electrode 523may be connected to the source electrode 533 depending on the type ofthin-film transistor.

The lower electrode 521, the intermediate electrode 522 and the firstinsulation layer 512B therebetween form a first capacitor C1, and theintermediate electrode 522, the upper electrode 523 and the additionalinsulation layer 513 therebetween forma second capacitor C2. Inaddition, the lower electrode 521 and the upper electrode 523 areconnected to each other, and thus the first capacitor C1 and the secondcapacitor C2 operate in parallel.

In this specification, a substrate refers to a member that supportsvarious elements formed thereon. The substrate may be comprised of aninsulation material. For example, the substrate may be, but is notlimited to, comprised of glass or plastic.

In this specification, an oxide semiconductor layer may include variousoxides that can be made conductivized. For example, in addition to theabove-mentioned indium-gallium-zinc-oxide (InGaZnO), the oxidesemiconductor may include: quaternary metal oxide such asindium-tin-gallium-zinc-oxide (InSnGaZnO) based material; ternary metaloxide such as indium-tin-zinc-oxide (InSnZnO) based material,indium-aluminum-zinc-oxide (InAlZnO) based material,indium-hafnium-zinc-oxide (InHfZnO) based material,tin-gallium-zinc-oxide (SnGaZnO) based material,aluminum-gallium-zinc-oxide (AlGaZnO) based material, andtin-aluminum-zinc-oxide based (SnAlZnO) material; binary metal oxidesuch as indium-zinc-oxide (InZnO) based material, tin-zinc-oxide (SnZnO)based material, aluminum-zinc-oxide (AlZnO) based material,zinc-magnesium-oxide (ZnMgO) based material, tin-magnesium-oxide (SnMgO)based material, indium-magnesium-oxide (InMgO) based material, andindium-gallium-oxide (InGaO) based material; mono metal oxide such asindium-oxide (InO) based material, tin-oxide (SnO) material, andzinc-oxide (ZnO) based material. The composition ratios between theelements in the above materials of the oxide semiconductor are notparticularly limited but may be variously determined.

In this specification, the conductive electrodes, i.e., the gateelectrode, the source electrode, the drain electrode, the intermediateelectrode, the upper electrode and the additional electrode may becomprised of, but are not limited to, molybdenum (Mo), aluminum (Al),chrome (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd) andcopper (Cu) or an alloy thereof. In addition, the conductive electrodes,that is, the gate electrode, the source electrode, the drain electrode,the intermediate electrode, the upper electrode and the additionalelectrode may be multiple layers comprised of a material selected from agroup consisting of molybdenum (Mo), aluminum (Al), chrome (Cr), gold(Au), titanium (Ti), nickel (Ni), neodymium (Nd) and copper (Cu) or analloy thereof.

Hereinafter, various embodiments of the organic light-emitting displaydevice according to the present invention will be described.

In some embodiments, the lower electrode, the first insulation layer andthe intermediate electrode form a first capacitor, and the intermediateelectrode, the second insulation layer and the upper electrode formasecond capacitor, wherein the first capacitor and the second capacitorare connected to each other in parallel to forma storage capacitor.

In some embodiments, capacitance of the first capacitor is larger thancapacitance of the second capacitor.

In some embodiments, the first insulation layer is thinner than thesecond insulation layer.

In some embodiments, the display device further comprises an additionalelectrode on the upper electrode, at least a part of the additionalelectrode overlapping the upper electrode.

In some embodiments, the additional electrode is connected to theintermediate electrode.

In some embodiments, the coplanar thin-film transistor further comprisesa gate insulation layer between the active layer and the gate electrode,wherein the first insulation layer is thinner than the gate insulationlayer.

In some embodiments, the coplanar thin-film transistor further comprisesan inter-insulation layer between the gate electrode and the sourceelectrode or the drain electrode, wherein the second insulation layer isthinner than the inter-insulation layer.

In some embodiments, the intermediate electrode is connected to the gateelectrode of the coplanar TFT.

In some embodiments, the upper electrode is electrically connected toone of the source electrode or the drain electrode of the coplanar TFT.

In some embodiments, the display device further comprises an organiclight-emitting element including an anode that is electrically connectedto the source or drain electrode connected to the upper electrode.

In some embodiments, the display device further comprises an organiclight-emitting element including an anode that is electrically connectedto the source or drain electrode connected to the upper electrode, and aconnection part interposed between the anode and one of the sourceelectrode or drain electrode, the connection part being comprised of thesame material as the additional electrode.

In some embodiments, the display device further comprises a plurality ofsub-pixels including a light-emitting region and a light-transmissiveregion, respectively, wherein the storage capacitor is positioned in thelight-emitting region.

In some embodiments, the storage capacitor in at least one of theplurality of sub-pixels has a size that is different from the size ofthe storage capacitor in another sub-pixel.

According to an exemplary embodiment of the present disclosure, there isprovided a method of manufacturing a displace device. The method ofmanufacturing a displace device comprises forming an oxide semiconductorlayer on a substrate, patterning the oxide semiconductor layer to forman active layer and a lower electrode portion spaced apart from theactive layer, conductivizing the lower electrode portion to form a lowerelectrode, forming a base insulation layer on the active layer and thelower electrode, forming a gate electrode and an intermediate electrodeon the base insulation layer, forming an additional insulation layerover the gate electrode and the intermediate electrode, the additionalinsulation layer having a contact hole, and forming a source electrode,a drain electrode and an upper electrode, wherein the upper electrodeconnected to the lower electrode via the contact hole in the additionalinsulation layer.

In some embodiments, the step of forming the gate electrode and theintermediate electrode comprises depositing a first conductive layer onthe base insulation layer, and patterning the first conductive layer toform the gate electrode and the intermediate electrode spaced apart fromthe gate electrode.

In some embodiments, the step of forming the source electrode, the drainelectrode and the upper electrode comprises depositing a secondconductive layer on the additional insulation layer, and patterning thesecond conductive layer to form the source and drain electrodes and theupper electrode.

The present invention has been described in more detail with referenceto the exemplary embodiments, but the present invention is not limitedto the exemplary embodiments. It will be apparent to those skilled inthe art that various modifications can be made without departing fromthe technical sprit of the invention. Accordingly, the exemplaryembodiments disclosed in the present invention are used not to limit butto describe the technical spirit of the present invention, and thetechnical spirit of the present invention is not limited to theexemplary embodiments. Therefore, the exemplary embodiments describedabove are considered in all respects to be illustrative and notrestrictive. The protection scope of the present invention must beinterpreted by the appended claims and it should be interpreted that alltechnical spirits within a scope equivalent thereto are included in theappended claims of the present invention.

What is claimed is:
 1. A display device, comprising: a coplanarthin-film transistor (TFT) on a TFT region of a substrate, the coplanarthin-film transistor comprising a gate electrode, an active layerincluding an oxide semiconductor, a source electrode and a drainelectrode; a lower electrode on a storage capacitor region, the lowerelectrode comprised of a same material as the active layer on thesubstrate, wherein the oxide semiconductor of the lower electrode isconductivized, wherein the lower electrode is separate from the sourceelectrode and the drain electrode and the lower electrode iselectrically connected to the source electrode or the drain electrode; afirst insulation layer on the lower electrode; an intermediate electrodecomprised of a same material as the gate electrode, the intermediateelectrode positioned on the first insulation layer and having at least apart overlapping with the lower electrode; a second insulation layer onthe intermediate electrode; an upper electrode comprised of a samematerial as the source electrode or as the drain electrode, the upperelectrode positioned on the second insulation layer and having at leasta part overlapping with the intermediate electrode; an additionalelectrode on the upper electrode, at least a part of the additionalelectrode overlapping the upper electrode, wherein the additionalelectrode has a direct electrical connection to the intermediateelectrode; and a connection part overlapping the source electrode or thedrain electrode and having a direct electrical connection to the sourceelectrode or the drain electrode, wherein the upper electrode isconnected to the lower electrode, wherein the lower electrode, theintermediate electrode and the upper electrode are located on thestorage capacitor region of the substrate, wherein the intermediateelectrode and the gate electrode are on a same plane and wherein theupper electrode and the source electrode or the drain electrode are on asame plane.
 2. The display device according to claim 1, wherein thelower electrode, the first insulation layer and the intermediateelectrode form a first capacitor, and the intermediate electrode, thesecond insulation layer and the upper electrode form a second capacitor,wherein the first capacitor and the second capacitor are connected toeach other in parallel to form a storage capacitor.
 3. The displaydevice according to claim 2, wherein capacitance of the first capacitoris larger than capacitance of the second capacitor.
 4. The displaydevice according to claim 3, wherein the first insulation layer isthinner than the second insulation layer.
 5. The display deviceaccording to claim 1, wherein the coplanar thin-film transistor furthercomprises a gate insulation layer between the active layer and the gateelectrode, wherein the first insulation layer is thinner than the gateinsulation layer.
 6. The display device according to claim 1, whereinthe coplanar thin-film transistor further comprises an inter-insulationlayer between the gate electrode and the source electrode or the drainelectrode, wherein the second insulation layer is thinner than theinter-insulation layer.
 7. The display device according to claim 1,wherein the intermediate electrode is connected to the gate electrode ofthe coplanar TFT.
 8. The display device according to claim 1, whereinthe upper electrode is electrically connected to one of the sourceelectrode or the drain electrode of the coplanar TFT.
 9. The displaydevice according to claim 8, further comprising an organiclight-emitting element including an anode that is electrically connectedto the source or drain electrode connected to the upper electrode. 10.The display device according to claim 1, wherein the connection partinterposed between an anode of an organic light-emitting element and oneof the source electrode or the drain electrode, the connection partbeing comprised of a same material as the additional electrode.
 11. Thedisplay device according to claim 2, further comprising a plurality ofsub-pixels including a light-emitting region and a light-transmissiveregion, respectively, wherein the storage capacitor is positioned in thelight-emitting region.
 12. The device according to claim 2, wherein thestorage capacitor in at least one of the plurality of sub-pixels has asize that is different from the size of the storage capacitor in anothersub-pixel.
 13. The display device according to claim 1, wherein thelower electrode has a resistivity of 10³ Ω/□ (ohm per square) orsmaller.
 14. An organic light emitting display device, comprising: acoplanar thin-film transistor (TFT) on a substrate, the coplanarthin-film transistor comprising a gate electrode, an active layerincluding an oxide semiconductor, a source electrode and a drainelectrode; a storage capacitor including a lower electrode comprised ofconductivized oxide semiconductor, wherein the lower electrode isseparate from the source electrode and the drain electrode and the lowerelectrode is electrically connected to the source electrode or the drainelectrode, a first insulation layer on the lower electrode, anintermediate electrode on the first insulation layer at a same plane asthat of the gate electrode, and having at least a part overlapping withthe lower electrode, a second insulation layer on the intermediateelectrode, an upper electrode on the second insulation layer at a sameplane as that of the source electrode or the drain electrode, and havingat least a part overlapping with the intermediate electrode, and anadditional electrode on the upper electrode, at least a part of theadditional electrode overlapping the upper electrode, wherein theadditional electrode has a direct electrical connection to theintermediate electrode; a connection part overlapping the sourceelectrode or the drain electrode and having a direct electricalconnection to the source electrode or the drain electrode; and anorganic light-emitting element including an anode that is electricallyconnected to the source or drain electrode of the coplanar TFT connectedto the upper electrode of the storage capacitor.
 15. The organic lightemitting display device according to claim 14, wherein the substrate hasa light-transmissive region and a light-emitting region, and wherein thecoplanar TFT, the storage capacitor and the organic light-emittingelement are positioned in the light-emitting region.
 16. The organiclight emitting display device according to claim 14, wherein thecoplanar TFT and the storage capacitor are not positioned in thelight-emitting region.
 17. The organic light emitting display deviceaccording to claim 14, wherein the storage capacitor in at least one ofa plurality of sub-pixels has a size that is different from the size ofthe storage capacitor in another sub-pixel.
 18. A semiconductor devicecomprising: a multi-layered capacitance structure, with alternatingelectrodes layers and insulating layers, having at least a firstcapacitor and a second capacitor connected in parallel to operatetogether as one capacitor, the multi-layered capacitance structureconfigured to accommodate a maximum number of sub-pixels per unit areafor a display panel while providing appropriate storage capacitancesufficient for applying relatively stable data voltage to a respectivesub-pixel of the display panel, and the multi-layered capacitancestructure comprising, an intermediate electrode at a same planar levelas that of a gate electrode of a thin film transistor (TFT) configuredto drive the respective sub-pixel, a lower electrode comprised ofconductivized oxide semiconductor at a same planar level as that of anoxide semiconductor layer of the TFT but disconnected therefrom, whereinthe lower electrode is separate from a source electrode and a drainelectrode of the thin film transistor (TFT) and the lower electrode iselectrically connected to the source electrode or the drain electrode,an upper electrode disposed at a same plane as that of the sourceelectrode or the drain electrode of the thin film transistor (TFT) andhaving at least a part overlapping with the intermediate electrode, andan additional electrode on the upper electrode, at least a part of theadditional electrode overlapping the upper electrode, wherein theadditional electrode has a direct electrical connection to theintermediate electrode.
 19. The semiconductor device of claim 18,wherein the multi-layered capacitance structure further comprises: afirst insulator layer on the lower electrode; a second insulator layeron the intermediate electrode; and the upper electrode on the secondinsulator layer, the first capacitor consisting of the lower electrode,the first insulator layer and the intermediate electrode, and the secondcapacitor consisting of the intermediate electrode, the second insulatorlayer and the upper electrode.
 20. The semiconductor device of claim 19,further comprising an organic light-emitting element including an anodethat is electrically connected to a source or drain electrode of thethin film transistor connected to the upper electrode.
 21. Thesemiconductor device of claim 20, further comprising a connection partinterposed between the anode and one of the source electrode or drainelectrode, the connection part being comprised of a same material as theadditional electrode.
 22. The semiconductor device of claim 20, whereinthe respective sub-pixel of the display panel has a light-transmissiveregion and a light-emitting region, and wherein the thin filmtransistor, the multi-layered capacitance structure and the organiclight-emitting element are only positioned in the light-emitting region.23. The semiconductor device of claim 18, wherein the lower electrode isconductivized as a result of a hydrogen plasma treatment process or ahelium plasma treatment process.
 24. A display device comprising: asubstrate having an array of pixels; each pixel having a pixel circuitthat includes a thin-film transistor (TFT) and a capacitor electricallyconnected to the TFT; the TFT having an active layer that corresponds toa lower electrode of the capacitor; the TFT having a gate layer thatcorresponds to an intermediate electrode of the capacitor; the TFThaving a source electrode or a drain electrode that corresponds to anupper electrode of the capacitor; and the TFT having a connection partthat corresponds to an additional electrode of the capacitor wherein thesource electrode or the drain electrode of the TFT and the upperelectrode of the capacitor are electrically connected; wherein a firstcapacitance is formed between the lower electrode of the capacitor andthe intermediate electrode of the capacitor, a second capacitance isformed between the intermediate electrode of the capacitor and the upperelectrode of the capacitor, a third capacitance is formed between theupper electrode of the capacitor and the additional electrode of thecapacitor.
 25. The display device of claim 24, wherein at least oneamong the active layer of the TFT and the lower electrode of thecapacitor, the gate layer of the TFT and the intermediate electrode ofthe capacitor, the source electrode or the drain electrode of the TFTand the upper electrode of the capacitor, and the connection part of theTFT and the additional electrode of the capacitor are made of a samematerial during a same manufacturing process using a halftone mask.